[PATCH 1/6] drm/crtc-helpers: Enforce sane set_config api

Daniel Vetter daniel.vetter at ffwll.ch
Fri Jun 14 15:13:11 PDT 2013


There's no point in trying to clean up after driver-bugs, so just blow
up. Furthermore it's an interface abuse to set no mode but have an fb
and aslo to try to set an fb without enough connectors. These two
spefici cases of interface abuse have been committed by the fb helper,
but that's been fixed meanwhile in

commit 7e53f3a423146745a4e4bb93362d488dfad502a8
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Mon Jan 21 10:52:17 2013 +0100

    drm/fb-helper: fixup set_config semantics

The i915 driver has been shipping since a while with these BUGs with
no reports, so should be save.

Note that this drops an ugly case where we clear crtc->fb behind the
upper levels back and so cause a refcounting mayhem, which Russell
Kins spotted while trying to hunt down a drm framebuffer leak.

Reported-by: Russell King <linux at arm.linux.org.uk>
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/drm_crtc_helper.c |   13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index f554516..e57cfec 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -565,14 +565,13 @@ int drm_crtc_helper_set_config(struct drm_mode_set *set)
 
 	DRM_DEBUG_KMS("\n");
 
-	if (!set)
-		return -EINVAL;
+	BUG_ON(!set);
+	BUG_ON(!set->crtc);
+	BUG_ON(!set->crtc->helper_private);
 
-	if (!set->crtc)
-		return -EINVAL;
-
-	if (!set->crtc->helper_private)
-		return -EINVAL;
+	/* Enforce sane interface api - has been abused by the fb helper. */
+	BUG_ON(!set->mode && set->fb);
+	BUG_ON(set->fb && set->num_connectors == 0);
 
 	crtc_funcs = set->crtc->helper_private;
 
-- 
1.7.10.4



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